Rheostat



(No Model.)

H. MGNULTA.

RHBOSTAT.

110,516,217. Patented Mar. 13,1894.

WITJVEIS'SES. I JV VEN TOR.

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UNITED STATES PATENT OFFICE.

HERBERT MCNULTA, OF BLOOMINGTON, ILLINOIS.

RH EOSTAT.

SPECIFICATION forming part of Letters Patent No. 516,217, dated March 13, 1894.

Application filed May 1, 1893. Serial 110.472,641. (No model.)

T0 all whom it may concern.-

Be it known that I, HERBERT MGNULTA, a citizen ot the United States, residing at Bloomington, McLean county, 1llinois,'haveinvented certain new and useful Improvements in Electrical Resistances, of which the following is a specification, reference being had to the accompanying drawings, in which- Figure 1 is a top or plan view. Fig. 2 is a sectional view on line 2 2 of Fig. 1. Fig. 3 is a side elevation. Fig. a is a plan view of one ot' the plates. Fig. 5 is an enlarged detail, being a vertical section through a portion of the resistance; and Figs. 6 and 7 are views similar to Figs. at and 5, showing a modiiied arrangement.

My invention relates to electrical resistances, and particularly to that class commonly known as contact resistances.

The objects ot my invention are to provide a new and improved resistance in which adequate means will be provided for cooling the surfaces of the plates, to provide tor the expansion incident to the heating of the plates, and to otherwise improve the construction of resistances of this class. I accomplish these objects as hereinafter specified and as illustrated in the drawings.

That which 1 regard as new will be set forth in the claims.

In the drawings-S indicates one of the resistances, which consists of plates D arranged in two rows, as shown in Fig. 1. rne plates 9 of each row are successively in contact with each other, but are spaced a short distance apart, which arrangement is provided for by swaging in each plate three or more projections 10, thereby providing corresponding recesses 11 on the opposite side of such plate. The projections 10 upon one plate fit into the recesses 11 in the next plate, and when the plates are secured together a compact body is secured.

As above stated, the plates 9 are arranged in two rows, and are secured together by end pieces 12-13, which are united by a bolt la which passes between the two rows of plates 9, as Shown in Fig. 1. The end pieces 12-13 are connected to connecting bars 15-16 respectively, to which bars other similar resistances may be connected, thereby forming a battery of resistances.

1718 indicate the end plates of the rows of plates, which end plates are provided with ears 19 bent at right angles to the main body ofthe plates to adapt them to fit upon the end pieces 12-13, as shown. Between the end plates and the end pieces are inserted strips 2O of insulating material, such as mica, to insulate the plates f) from such end pieces. The end plates 17 at one end ot the rows of plates are provided with projections 10 and the end plates 1S at the other ends of said rows are provided with depressions 11, to provide for causing said plates to t snugly against the adjoining plates.

To provide for the expansion of the plates 9 due to the heat generated by the passage of the current through them, the bolt 14 is provided at its en ds with springs 21, which bear against the head and nut of the bolt and the adjacent portions of the end pieces 12 or 13. As the plates 9 expand the springs 21 will permit the end pieces 12--13 to separate slightly, and will cause them to approach each other as the plates become cool again. By this construction the pressure ot the plates upon each other will be substantially uniform at all times, and the resistance willnot, there- Jfore, be caused to vary materially by ordinary variations in the current passed through the plates. B y separatin the plates as shown air is permitted to pass freely between them, thereby preventing over-heating.

The end plates 17-18 are also provided with ears 22, by means ot which the connections with the electric wires maybe made. As shown in Fig. 3, one or more of the intermediate plates may also be provided with an ear 22, by means of which the number of plates through which the current is passed may be varied asdesired.

1n Figs. G and 7 1 have shown modified plates, in whioh,-in addition to the projections 10 above described,three smaller projections 25 are provided, thereby forming corresponding depressions 2t in the opposite side of the plate. The depressions 24: are

also in triangular form, forming a triangle equal to that formed by the projections 10. The arrangement is such that in setting up the resistance the projections 10 of one plate will lie in the depressions 24; ot the next plate. The projections 23 do not project far enough IOO to touch the surface of the adjacent plate. By this construction the plates 9 are spaced a greater distance apart than in the construction shown in Figs. 4. and 5, and the possibility of the flat surfaces of the plates being moved into contact with each other owing to the expansion caused by the passage of anextraordinary current through the resistance, is thereby prevented. f

I do not Wish to limit myself to providing each plate with three contact projections, as the number may beyaried if desired. I prefer, however, to use/three.

An important advantage in my improved resistance lies in the fact that its construction is Very inexpensive, since the plates 9 may be very rapidly stamped out and are immediately ready for assembling to form the resistance.

That which I claim as my invention, and desire to secure by Letters Patent, is-

1. In an electrical resistance, the combination with a series of plates, each ot' said plates having projections adapted to lie in contact with an adjacent plate, of means for binding said plates together, substantially as described.

2. In an electrical resistance, the combination with a series of plates, each of said plates having a series of projections upon one face and a series of indentations in the other face, of devices for binding said plates together, substantially as described.

3. In an electrical resistance, the combination with a series of plates, each of said plates having a series of projections uponone face and a series of coincident indentations in the other face, the projections upon one plate being adapted to t into the indentations in the adjacent plate, of means for binding said plates together, substantially as described.

4. An electrical resistance, consisting of end pieces, a series of plates insulated from the end pieces and spaced a distance apart so that air can circulate between the plates, means for electrically connecting the plates, and a ULUHA.

bolt connecting the en d pieces, substantially as described.

5. An electrical resistance, consisting of a series of plates held together bya binding device and locked in engagement one to the other against independent lateral movement yin any direction in planes parallel with the adjacent surfaces of the plates, substantially as described.

6. An electrical resistance, consisting of a pile of plates each of which contacts with an adjacent plate by contact projections, substantially as described. 7. An electrical resistance, consisting of a series of plates engaged with one an other and yieldingly held together by a binding device, substantially as described.

8. In an electrical resistance, the'combination with a series of plates in contact with each other, of yielding devices binding said plates together, whereby a substantially constant pressure upon said plates will be maintained, substantially as described.

9. lIn an electrical resistance, the combination with a series of plates arranged in rows, and end pieces at the ends of said rows, of a bolt extending between the rows of plates and connecting said end pieces, substantially as described.

l0. In au electrical resistance, the combination with a series of plates arranged in rows, and end pieces at the ends of said rows, of a bolt connecting said end pieces, and a spring upon said bolt, whereby expansion of said plates will be permitted, substantially as described.

1l. An electrical resistance plate consisting of a plate 9 having a series ot projections l0 upon one face, and a series of depressions in the other face, substantially as described.

HER BERT MCNULTA.

Witnesses:

J. L. JACKsoN, A. I-I. ADAMS. 

